Sulfur chemistry in the envelope of VY Canis Majoris: Detailed analysis of SO and SO{sub 2} emission
Detailed radiative transfer modeling has been carried out for SO{sub 2} and SO originating in the envelope of the O-rich supergiant star VY Canis Majoris (VY CMa). A total of 27 transitions of SO{sub 2} and 7 transitions of SO lying in the energy range 3.0-138.2 cm{sup –1} were analyzed using a new non-LTE radiative transfer code that incorporates non-spherical geometries. The spectra were primarily obtained from the Arizona Radio Observatory (ARO) 1 mm spectral survey of VY CMa, conducted with the Submillimeter Telescope; additional lines were measured with the ARO 12 m antenna at 2 and 3 mm. SO{sub 2} and SO were found to arise from five distinct outflows within the envelope, four which are asymmetric with respect to the star. Three flows arise from high-velocity red-shifted material, one from a blue-shifted wind, and the final from a classic 'spherical' expansion. In the spherical component, the peak fractional abundance, relative to H{sub 2}, of both molecules is f ∼ 2.5 × 10{sup –7} at r ∼ 25 R {sub *}, and steadily decreases outward. SO{sub 2} appears to be a 'parent' molecule, formed near the stellar photosphere. In the asymmetric outflows, both SO and SO{sub 2} are more prominent at large stellar radii in dense (10{sup 6}-10{sup 7} cm{sup –3}), clumpy material, achieving their maximum abundance between 200 and 600 R {sub *} with f ∼ 3.0 × 10{sup –8}-1.5 × 10{sup –7}. These results suggest that in the collimated outflows, both species are either produced by shock chemistry or are remnant inner shell material swept up in the high-velocity winds.
- OSTI ID:
- 22342037
- Journal Information:
- Astrophysical Journal, Vol. 778, Issue 1; Other Information: Country of input: International Atomic Energy Agency (IAEA); ISSN 0004-637X
- Country of Publication:
- United States
- Language:
- English
Similar Records
EXOTIC METAL MOLECULES IN OXYGEN-RICH ENVELOPES: DETECTION OF AlOH (X{sup 1}{sigma}{sup +}) IN VY CANIS MAJORIS
ARCSECOND RESOLUTION MAPPING OF SULFUR DIOXIDE EMISSION IN THE CIRCUMSTELLAR ENVELOPE OF VY CANIS MAJORIS